Abstract In this paper, our objectives are: (i) To provide an outline of the modal version of the ontological proof proposed by Charles Hartshorne, one version which emp- hasizes the unique logical properties of the notion of God, which demonstrates that the proof leaves open only two coherent alternatives, positivism and modal theism, and which, in order to cope successfully with positivism, appeals to a process phi- losophy inspired by Whitehead which accepts contingent properties, as well as essential ones, in God. (ii) To evaluate Hartshorne’s position, defending it against some usual misunderstandings and suggesting some improvements, in concrete, an assessment of Russell’s project of reducing modal values to scope-words, and the development of an iterative conception of modality. (iii) To vindicate Hartshorne’s philosophical attitude, a circumspect rationalism which tries to make sense of recal- citrant phenomena without yielding to epistemological or conceptual deflationism, and which underlines that experience has a rational basis, but that reason cannot exhaust experience. Keywords: Abstract-concrete paradox, Actuality, Existence, Hartshorne, Immanent Causality, Logical space, Positivism, Unconditional necessity. Resumen Las pretensiones del autor son: (i) Describir la versión modal de la prueba onto- lógica propuesta por Charles Hartshorne, una versión que enfatiza la anomalía LOGOS. Anales del Seminario de Metafísica Vol. 46 (2013): 125-147 ISSN: 1575-6866 http://dx.doi.org/10.5209/rev_ASEM.2013.v46.42867 125 Existence and actuality: Hartshorne on the ontological proof and immanent causality Existencia y actualidad: prueba ontológica y causalidad inmanente de acuerdo con Hartshorne Modesto M. GÓMEZ ALONSO (Universidad Pontificia de Salamanca) Recibido: 08/02/2012 Aceptado: 07/12/2012